Adopting the load and resistance factor design format, the design method for steel jaeket platform structures is developed. Firstly, the limit state equations and design format for steel jacket platform structures are...Adopting the load and resistance factor design format, the design method for steel jaeket platform structures is developed. Firstly, the limit state equations and design format for steel jacket platform structures are introduced. Then, the ratio of live load effect to dead load effect is estimated. The target reliabilities for design of offshore structures in China offshore area are calibrated by past practice in API RP2A-WSD code. The load and resistance factors are optimized by minimizing the difference within the target reliability and the resulting reliability over the range of load effect ratios. Considering the concurrence of different loads, load combination factors are obtained through an optimization process, and the relation between the load combination factor and load correlation coefficient is established. Finally, the design formulae for steel jacket structures in China offshore area are recommended.展开更多
A new combined steel lead damper (NCSLD) was presented. Construction and working mechanism of NCSLD were introduced,pseudo-static tests of the small size dampers which would be used in the subsequent shaking table tes...A new combined steel lead damper (NCSLD) was presented. Construction and working mechanism of NCSLD were introduced,pseudo-static tests of the small size dampers which would be used in the subsequent shaking table tests were carried out for the study of mechanical properties of NCSLD using electro-hydraulic servo press-shear machine. Processing technology of the damper was improved. Shaking table tests under two-dimensional excitation on structural aseismic control of a one-story structure model were carried out using the small size NCSLD; parameters of the structure and shaking table were also introduced. Results indicate that process improvement is beneficial to the implementation of working mechanism of the damper,NCSLD has full hysteresis loop which takes on bilinearity,NCSLD has obvious energy dissipation effect and it can control structural seismic response effectively.展开更多
The microstructure and properties of a combined precipitation hardening ultrahigh strength steel with nano-sized carbides and intermetallics were studied systematically.The results show that after tempering at 300℃lo...The microstructure and properties of a combined precipitation hardening ultrahigh strength steel with nano-sized carbides and intermetallics were studied systematically.The results show that after tempering at 300℃lots ofε-carbides are precipitated in the martensite,the strength rises and the toughness falls slightly.After tempering at 430℃,much coarser cementite lamina are precipitated in martensitic laths,which causes the impact toughness falls to the minimum value.With temperature further increasing the cementites are dissolved and M_2C carbides,β-NiAl intermetallics and reverse austenite begin to precipitate.The tensile strength and yield strength achieve the peak value at 470℃,490℃respectively.The tested steel achieve a tensile strength of 2 120 MPa,a yield strength of 1 950 MPa and impact energy of 54 J/cm^2 after optimum tempering at 510℃.When tempering temperature is above 530℃the M_2C carbides and reverse austenite is coarsening.After tempering at 560℃the reverse austenite reaches the maximum volume fraction in present work.展开更多
文摘Adopting the load and resistance factor design format, the design method for steel jaeket platform structures is developed. Firstly, the limit state equations and design format for steel jacket platform structures are introduced. Then, the ratio of live load effect to dead load effect is estimated. The target reliabilities for design of offshore structures in China offshore area are calibrated by past practice in API RP2A-WSD code. The load and resistance factors are optimized by minimizing the difference within the target reliability and the resulting reliability over the range of load effect ratios. Considering the concurrence of different loads, load combination factors are obtained through an optimization process, and the relation between the load combination factor and load correlation coefficient is established. Finally, the design formulae for steel jacket structures in China offshore area are recommended.
基金Sponsored by the National Natural Science Foundation of China (Grant No. 50508012)Science &Technology Plan Project of Guangdong Province(Grant No. 20055190030)+1 种基金Key Basic Research Project of Science and Technology Ministry (Grant No. 2004CCA03300)Science &Technology Project of Guangzhou Education Bureau(Grant No.08C05)
文摘A new combined steel lead damper (NCSLD) was presented. Construction and working mechanism of NCSLD were introduced,pseudo-static tests of the small size dampers which would be used in the subsequent shaking table tests were carried out for the study of mechanical properties of NCSLD using electro-hydraulic servo press-shear machine. Processing technology of the damper was improved. Shaking table tests under two-dimensional excitation on structural aseismic control of a one-story structure model were carried out using the small size NCSLD; parameters of the structure and shaking table were also introduced. Results indicate that process improvement is beneficial to the implementation of working mechanism of the damper,NCSLD has full hysteresis loop which takes on bilinearity,NCSLD has obvious energy dissipation effect and it can control structural seismic response effectively.
文摘The microstructure and properties of a combined precipitation hardening ultrahigh strength steel with nano-sized carbides and intermetallics were studied systematically.The results show that after tempering at 300℃lots ofε-carbides are precipitated in the martensite,the strength rises and the toughness falls slightly.After tempering at 430℃,much coarser cementite lamina are precipitated in martensitic laths,which causes the impact toughness falls to the minimum value.With temperature further increasing the cementites are dissolved and M_2C carbides,β-NiAl intermetallics and reverse austenite begin to precipitate.The tensile strength and yield strength achieve the peak value at 470℃,490℃respectively.The tested steel achieve a tensile strength of 2 120 MPa,a yield strength of 1 950 MPa and impact energy of 54 J/cm^2 after optimum tempering at 510℃.When tempering temperature is above 530℃the M_2C carbides and reverse austenite is coarsening.After tempering at 560℃the reverse austenite reaches the maximum volume fraction in present work.
